Circulation and Gas Exchange

Why is the circulatory system necessary?  TRANSPORTATION!  Diffusion is not fast enough to transport chemicals throughout an animal’s body  The circulatory system transports fluid throughout the body This solves the problem of diffusion by ensuring that no substance had to diffuse far to enter or leave a cell Subway stop analogy…

Open vs. Closed Circulatory Systems  In open circulatory systems, hemolymph bathes the internal organs directly Insects, arthropods, mollusks  In closed circulatory systems, blood is confined to vessels Blood exchanges materials with the ISF bathing the cells Earthworms, squids, octopuses, vertebrates

Open vs. Closed Circulatory Systems

Adaptations of the Vertebrate Circulatory System  Fish Heart with 2 chambers (one atrium, one ventricle)  Amphibians (frogs) 3-chambered heart (two atria, one ventricle)  Birds/Mammals 4-chambered heart (two atria, two ventricles)

Adaptations of the Vertebrate Circulatory System

The Heart  About the size of a clenched fist  Made up of mostly cardiac muscle tissue  Diagram!  Atria have thin walls, ventricles have thicker walls Why??

The Heart: Structure and Function  AV Valves: Located between each atrium and ventricle Keep blood from flowing back into the atria  Semilunar Valves: Located at the exits of the heart (at the bottom of each ventricle) Prevent blood from flowing back into the ventricles

The Human Heart

Blood Vessels  Arteries carry blood away from the heart to organs throughout the body Arteries are thicker than veins…why??  Veins return blood to the heart Categorized by direction of flow, NOT whether or not they contain oxygen  Capillaries are microscopic vessels with very thin, porous walls  DIAGRAM!!

Capillary Exchange  The capillary wall is a single layer of flattened cells  The transfer of substances occurs between the capillaries and the interstitial fluid (which bathes the cells) This occurs by bulk flow, the movement of fluid due to pressure Water, sugars, salts, oxygen, and urea pass through the capillary walls

Capillary Exchange

Control of the Heart  Cardiac muscles contract (systole) and relax (diastole) in a rhythmic cycle  The sinoatrial node (SA node), also known as the pacemaker, maintains the heart’s pumping rhythm by setting the rate at which all cardiac muscles contract

Control of the Heart

The Structure of Blood  Blood is made up of plasma, red blood cells, white blood cells, and platelets  Plasma, which makes up about 55% of blood volume, is mostly water Plasma also contains antibodies Plasma also contains fibrinogens, proteins that act as clotting factors  Fibrinogen (inactive) is a protein in blood that is converted into fibrin (active), when needed Hemophilia is an inherited disorder, characterized by excessive bleeding from minor cuts and bruises People with hemophilia can die from minor cuts

The Structure of Blood  Red Blood Cells (Erythrocytes) The human body contains 25 trillion red blood cells Major function is to transport oxygen Contains hemoglobin, an iron- containing protein that carries oxygen Red blood cells are produced in the bone marrow

The Structure of Blood  White blood cells (leukocytes) Major function is to fight infection 5 major types  Monocytes, neutrophils, basophils, eosinophils, lymphocytes White blood cells spend most of their time patrolling through the ISF and the lymphatic system, where most of the battles against pathogens are waged

The Structure of Blood  Platelets Platelets are fragments of cells Platelets enter the blood and function in the process of blood clotting

Blood: An Overview

Cardiovascular Disease  Cardiovascular disease (diseases of the heart and blood vessels) cause more than half of all deaths in the US  Heart attack: Death of cardiac muscle tissue as a result of blockage of a coronary artery  Stroke: Death of nervous tissue in the brain, resulting from blockage of arteries in the head

Artherosclerosis

The Respiratory System  What is its function? Why is it necessary? GETS oxygen for the body  Needed for cellular respiration GETS RID of carbon dioxide  Produced during cellular respiration  Characteristics/Requirements of ALL Gas Exchange Mechanisms: MOIST membranes High surface area-to-volume ratio  An animal’s respiratory surfaces must be large enough to provide oxygen and expel carbon dioxide for the entire body

Respiration in Non-Mammals  Small animals (earthworms, etc.) exchange gases by diffusion across its general body surface  Gills are outfoldings of the body surface specialized for gas exchange for aquatic organisms Blood flowing through the capillaries picks up oxygen from the water

Countercurrent Exchange (Aquatic Animals)  Countercurrent exchange allows for the efficient transfer of oxygen to the blood As blood flows through the capillary, it becomes more and more loaded with oxygen Steep concentration gradient allows for efficient uptake of oxygen

Countercurrent Exchange

Tracheae  The respiratory system used by insects  Tracheae are air tubes that branch throughout the insect body  The finest branches of the tracheae extend to the surface of nearly every cell, where gas is exchanged by diffusion

Lungs  Lungs are found in terrestrial vertebrates Reptiles, birds, mammals, amphibians  Lungs of mammals have a large enough surface area to carry out gas exchange for the entire body How do the gases get from the lungs throughout the rest of the body, though?? The circulatory system transports the gases throughout the body after they’re exchanged in the lungs

Human Respiratory System

 Air enters the lungs by a system of branching ducts Nostrils Pharynx Larynx Trachea 2 bronchi Bronchioles Alveoli  DIAGRAM

Alveoli  Alveoli are clusters of air sacs at the end of bronchioles Alveoli have thin epithelium, which serve as the respiratory surface Oxygen diffuses from the alveoli into the web of capillaries around each alveolus The capillaries then transfer the oxygen throughout the body, via the circulatory system  ALVEOLI/CAPILLARY DIAGRAM